At 10 a.m. on January 6, the first DC UHV project in Hebei Province, the Shanxi Jinbei-Jiangsu Nanjing ±800 kV UHV DC transmission line project (Hebei Section 1), constructed by Hebei Electric Power Transmission & Transformation Company, began hoisting tower pieces for Tower N1230, marking the project's entry into the tower assembly phase. During nearly four months of foundation construction, the participating employees worked together to overcome difficulties, including continuous rain, fog and haze, a large construction volume, and a complex construction environment, leaving a proud chapter of dedicated UHV grid construction on the ancient land of Yanzhao.
The project is an important part of the "three AC and three DC" UHV backbone grid of the Hebei South Power Grid, the first UHV DC transmission line project in the province, and a key project for air pollution control. This section is 223.699 km long, with 436 foundations and towers, passing through Xingtai and Handan prefecture-level cities, 10 counties, 41 townships, and 181 natural villages. It needs to cross the Beijing-Guangzhou high-speed railway, the Beijing-Guangzhou electrified railway and other railways 4 times, cross 1000 kV UHV lines once, cross ±600 kV and 500 kV lines 6 times, and cross multiple power lines above 110 kV. Foundation types include rock-embedded foundations, excavated foundations, column-slab foundations, inclined column-slab foundations, cast-in-place pile foundations, etc. Numerous crossings and complex terrain bring great resistance to construction.
In the early stage of construction, the project department, in view of the long line, many foundations, many administrative villages passed through, and complex construction environment, set up one main project department, three branches, and seven construction teams under them to manage their respective areas. In terms of organizational structure, according to the State Grid DC Department, main management personnel, full-time safety officers, quality inspectors, and accompanying personnel were assigned to the project department for detailed management.
Every day before work, the management personnel of the project department go to each work point to check the implementation of safety technical measures. In the evening, they persist in organizing everyone to hold a post-shift meeting to summarize the day's work and arrange the next day's work, which has become the norm. The teams also hold weekly analysis meetings to carefully analyze and find problems in the work, formulate targeted rectification measures, and continuously optimize on-site work plans.
In response to the difficulty of coordination with local villagers, the project department assigned sufficient coordination personnel, closely relying on local companies and local governments to actively carry out coordination work, laying a solid foundation for the rapid progress of construction.
Facing the situation of many foundation types and scattered construction teams, the project department selected different foundation types to undertake sample tasks for the same type of foundation, achieving unified control, unified standards, sample guidance, and solidified application across the entire line in terms of scheme design, finished product process control, and on-site safe and civilized construction management. At the same time, at monthly meetings, PPT was used to reward the excellent and punish the poor, ensuring that individual projects are excellent at the first attempt and excellent in the process.
It is precisely the scientific organization and deployment of the project department that enabled all construction teams to advance together and flourish, ensuring the smooth progress of the foundation engineering.
During the construction process, the project department actively carried out scientific and technological innovation activities. A QC group was established according to construction difficulties to solve construction problems encountered in the project. After receiving the foundation construction drawings, the inclined column large slab foundation adopted suspended inserted angle steel, and how to fix the angle steel was a problem. To this end, the construction project team held a special meeting. "We can use false legs," said Yin Quanjun at the meeting, which enlightened everyone. They immediately had an idea, began to draw sketches, simulate, and calculate, and developed auxiliary positioning angle steel. After repeated calculations and verification, they added variable cross-section connections, saving materials, facilitating construction, and effectively solving the difficulty of controlling the opening of suspended main angle steel. Through the promotion of 43 inclined column large slab foundations across the entire line, the time for fixing and aligning the main angle steel was greatly shortened, construction accuracy was improved, and the smooth progress of inclined column large slab foundations was ensured. For the cast-in-place pile foundations that require anti-corrosion treatment in this project, anti-corrosion paint needs to be applied half a meter below the ground, and the formwork must be supported on the freshly poured soft foundation concrete, making alignment particularly difficult. Qiu Aimin, captain of the fourth construction team, together with the cast-in-place pile construction personnel, through experiments and improvements, developed an alignment bracket for cast-in-place pile formwork using waste steel bars to fix the relative position of the formwork, greatly shortening the adjustment time and ensuring that pouring is completed before initial setting. On this basis, the technical group of the project department made further improvements, using existing straight thread connection technology to make a combined cast-in-place pile formwork alignment bracket. It has a simple structure, is convenient to transport, can be reused, and can be applied to cast-in-place piles of all pile diameters in this project. It has been promoted in engineering construction with good results. "The quality management systems of all responsible entities in this project are sound and operate effectively, and the construction quality process management is under control." On December 28, 2015, the project successfully passed the first stage quality supervision and inspection before tower assembly organized by the Electric Power Engineering Quality Supervision Station.